Displacement not working correctly
With the Displacement node plugged into the Material Output you're trying to give real displacement to your object. It won't work if you don't give it enough topology, you need to subdivide it.

Also, the Image Texture is supposed to be plugged into the Displacement Height input.

I'm not sure I would use this kind of effect for a hardsurface object though, it works fine for organic object but here it will require a very high-poly mesh, you should try to fake 3D with a Bump node.

Here I've subdivided the mesh to get the Displacement effect:



Here it's a low-poly with 3D faked with a Bump node (plugged into the Normal input of the Diffuse this time):